You’ve just had a fight with your partner or a confrontation with a colleague. Now your heart’s racing, and you’re struggling to think straight. What should you do?

Psychologists are not short on ideas for how to calm yourself down after a stressful experience. Seek out a friend? Yes, there’s good evidence that can help. But what if there’s no friend to hand? You could try to alter your view of what just happened from “Disaster!” to “Not really so bad”.

But it can be difficult to engage in this kind of “cognitive reappraisal” when you’re in the immediate aftermath of a stressful event – perhaps because acute stress compromises the neural circuitry that’s involved in emotion regulation.

Your brain needs help if it’s to quickly regain control. And, according to a new study published in Nature Human Behaviour, you can provide it by thinking back over good times.

Mauricio Delgado and Megan Speer at Rutgers University, US, made 134 volunteers feel stressed by videoing them while they plunged their hands into icy water. Some then spent 14 seconds reminiscing about a positive experience (like visiting Disneyland) while others reflected on an emotionally neutral event (such as getting luggage ready for the trip).

Afterwards, the group who’d recalled happy memories felt better, but not only that: the expected rise in their levels of the stress hormone cortisol was only 15 per cent, on average, of the surge observed in the neutral memory group. Thinking about happy memories, then, went right to the heart of the physiological stress response.

To explore how, Delgado and Speer used the same technique as before to stress a fresh group of volunteers and then had them reminisce about their own positive or neutral experiences while they scanned their brains using fMRI. The pair found that recollecting good, but not neutral, memories was associated with increased activity in prefrontal brain regions associated with emotion regulation and cognitive control – the same regions suppressed by acute stress – as well as in corticostriatal regions associated with the processing of reward.

The idea that thinking about positive past events, including achievements or successes, can help to improve ongoing mood and resilience to stress is certainly not new. But showing that simply recalling happy memories can combat acute stress at a physical level is important, since there’s plenty of research finding that people who tend to calm down physiologically soon after stressful events are generally healthier, both physically and psychologically, over the long term.

There are a few caveats. This work was on healthy adults. People with depression usually find it hard to recall positive memories, so this technique may not work well for them. And it’s not clear yet whether any technique that makes you feel positive emotions would be effective or if there’s something special about reminiscing. But this is at least a simple method, and one that in theory many people could try.